forked from mpusz/mp-units
80 lines
2.6 KiB
ReStructuredText
80 lines
2.6 KiB
ReStructuredText
Quick Start
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===========
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Here is a small example of possible operations::
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#include <units/isq/si/area.h>
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#include <units/isq/si/frequency.h>
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#include <units/isq/si/speed.h>
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using namespace units::isq::si;
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// simple numeric operations
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static_assert(10_q_km / 2 == 5_q_km);
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// unit conversions
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static_assert(1_q_h == 3600_q_s);
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static_assert(1_q_km + 1_q_m == 1001_q_m);
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// dimension conversions
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static_assert(1_q_km / 1_q_s == 1000_q_m_per_s);
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static_assert(2_q_km_per_h * 2_q_h == 4_q_km);
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static_assert(2_q_km / 2_q_km_per_h == 1_q_h);
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static_assert(2_q_m * 3_q_m == 6_q_m2);
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static_assert(10_q_km / 5_q_km == 2);
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static_assert(1000 / 1_q_s == 1_q_kHz);
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.. admonition:: Try it on Compiler Explorer
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`Example #1 <https://godbolt.org/z/shcohY>`_
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This library requires some C++20 features (concepts, classes as
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:abbr:`NTTP (Non-Type Template Parameter)`, ...). Thanks to them the user gets a powerful
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but still easy to use interface where all unit conversions and dimensional analysis can be
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performed without sacrificing on accuracy. Please see the below example for a quick preview
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of basic library features::
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#include <units/format.h>
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#include <units/isq/si/speed.h>
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#include <units/isq/si/international/speed.h>
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#include <units/quantity_io.h>
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#include <iostream>
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using namespace units::isq;
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constexpr Speed auto avg_speed(Length auto d, Time auto t)
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{
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return d / t;
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}
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int main()
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{
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using namespace units::isq::si::literals;
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using namespace units::isq::si::unit_constants;
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constexpr Speed auto v1 = 110 * (km / h);
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constexpr Speed auto v2 = avg_speed(220_q_km, 2_q_h);
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constexpr Speed auto v3 = avg_speed(si::length<si::international::mile>(140), si::time<si::hour>(2));
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constexpr Speed auto v4 = quantity_cast<si::speed<si::metre_per_second>>(v2);
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constexpr Speed auto v5 = quantity_cast<si::metre_per_second>(v3);
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constexpr Speed auto v6 = quantity_cast<int>(v5);
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std::cout << v1 << '\n'; // 110 km/h
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std::cout << fmt::format("{}", v2) << '\n'; // 110 km/h
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std::cout << fmt::format("{:*^14}", v3) << '\n'; // ***70 mi/h****
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std::cout << fmt::format("{:%Q in %q}", v4) << '\n'; // 30.5556 in m/s
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std::cout << fmt::format("{0:%Q} in {0:%q}", v5) << '\n'; // 31.2928 in m/s
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std::cout << fmt::format("{:%Q}", v6) << '\n'; // 31
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}
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.. admonition:: Try it on Compiler Explorer
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`Example #2 <https://godbolt.org/z/dY1dEd>`_
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.. seealso::
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You can find more code examples in the :ref:`examples:Examples` chapter.
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